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The difference between ISO200 and ISO160 isn't controllable be the user. Its done on camera. If you underexpose, it won't help. Setting exposure compensation to something probably won't do anything either and wouldn't be worth the hassle.

Use native ISOs for best image quality. Native being 100, 200, 400, 800...
Intermediate ISO gains are done by software, therefore reducing highlight dynamic range. Sure there might be a bit less noise at 160, 320 and so on, but highlights clip earlier.

People shooting at ISO 160 are loosing 1 1/3 of a stop in highlight detail (compared to ISO200 with HTC ON). Thatīs actually a lot.

Itīs being common knowledge that at least in lower Canon models, intermediate ISO gains are done by software (when the camera or your PC converts from RAW-RGB): for all of the +2/3rd ISO stop levels, they are actually using the next higher full-stop ISO level, and dropping the EV by 1/3rd after the A/D conversion!

So yes, ISO160 has less noise than any other ISO setting BUT the dynamic range is shifted (highlights clip earlier).

I just did some test today with a 5D. Exactly as expected, the intermediate ISOs clip highlights detail earlier (1/3 of a stop). And HTP gets you another stop. So for example, shooting ISO 400+HTC gives you +1 1/3 stops more in highlight detail compared to ISO 640 given the same mid grey exposure.